How Can a Dirty Filter Cause Water Leaks in Your Furnace?

Feb 17, 2015

Air filters are designed to protect HVAC systems from particles and microorganisms in household air. However, if a filter is clogged, it can’t do its job properly and can actually harm your HVAC system. This begs the questions of whether or not a dirty air filter can cause water leaks in your furnace. Read on to find out.

Dirty Air Filters

A dirty air filter can restrict airflow to your furnace blower, causing several problems related to performance, efficiency, comfort and water leaks.

In cool mode, a dirty filter can reduce airflow, resulting in ice accumulation on A/C coils. Free airflow is required across the coil to instigate heat exchange and keep all components functioning normally. As the ice melts, it carries debris with it into the drip pan and drain line, which may cause a clog and water overflow. Water in your furnace can cause rust and corrosion.

A dirty filter allows contaminants to bypass and stick to components. Debris, dirt and even mold and mildew growth can clog the drain line. This too can cause water to overflow the drip pan and leak inside your home and furnace.

Reduced airflow can cause condensation inside air ducts, some of which can drip into the furnace and cause rust.

In heat mode, restricted airflow due to a clogged filter can cause your furnace to overheat and shut down. Once it has cooled, it will restart. However, it will repeat the quick cycling until the filter is changed or the furnace fails.

Preventive Maintenance

A furnace connected to a central air unit has an evaporator coil attached to it. This is the normal configuration, but water damage, such as rust, corrosion and water stains, can occur if the evaporator coil isn’t well maintained. Make sure you schedule preventive maintenance each year with your HVAC professional to keep your A/C and furnace in tip-top shape.

Our goal is to help educate our customers in Orlando, Florida and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about furnaces and other HVAC topics, download our free Home Comfort Resource guide.